In data centers or information system in enterprises that operate a plurality of application systems using limited computers, resources have been effectively used using provisioning of a server. The provisioning of the server is a process that changes the configuration of a pool server shared by a plurality of application systems to the configuration of a specific application server. The configuration changing process includes a switching process of an OS, an application setup process, and a setting changing process of a network apparatus or a storage device.
A provisioning function is sold and provided as a software product. However, when the provisioning function is actually used, a process time that is related to provisioning becomes a problem. For example, the provisioning function is used in a large-scale complicated system, a time of several minutes or more is needed to execute the switching process of the OS or the configuration changing process of the network. For this reason, when a scale of a system becomes increased and complicated, it becomes difficult to quickly perform the provisioning of the server when an accidental load change or failure occurs.
In Patent Document 1, an example of a provisioning system for a typical load balancing is disclosed. The system disclosed in Patent Document 1 is a system that subjects a request from a client computer to a Web server and performs a load balancing using a load balancer (LB). The system increases and decreases the number of Web servers to be a target of load balancing in accordance with a load situation, and optimizes the number of operating servers. In this system, since a simple system that is composed of a Web server is basically used, the provisioning is completed by only a boot process of an OS application.
Meanwhile, a number of Web application systems include a plurality of server systems, such as an application server (AP server) or a database server (DB server) and a managing server that manages the application server or a network. Accordingly, when the AP sever is subjected to the provisioning, it is needed to execute not only the boot process of the OS and the application but also a connection setting process to a DB server or a registering process to a managing server, an update application process of the application, and the configuration changing process of the network. For this reason, when the method disclosed in Patent Document 1 is applied to the Web application system, an overhead related to processes other than the boot process of the OS and the application cannot be ignored.
Further, in the method disclosed in Patent Document 1, the configuration where the OS and the application image are stored in a storage area network (SAN) and shared is basically used. Such a system configuration cannot be generally used at a current point of time. When the system configuration is applied to the existing system, the system needs to be reconstructed. For example, a method in which a blade system where the SAN is integrated is newly introduced is considered, but this method is not suitable for an object of effectively using the system during the operation.
In Patent Document 2, as a method for reducing a time related to setting of a computer, a method where an OS or an application is operated on a shared computer to generate a standby state is disclosed. In the method disclosed in Patent Document 2, a standby (hot standby) is not maintained as a specific application system, but a standby is maintained in a middle state that can be set in another application system. In this way, it is possible to reduce a computer setting time to a plurality of application systems on the average.
Patent Document 2 discloses a method to speed up provisioning of a pool server that is not used as a specific application system. However, it is not possible to speed up provisioning for switching the pool server, which is being used as a portion of the application system, into another application system.
Meanwhile, in order to integrate distributed servers into one server and decrease a cost or management work, it has been recently reported a case in which a virtualization technology of a server is introduced. Among various virtualization technologies, in a virtualization method that uses a virtual machine monitor shown in Non-Patent Document 1, a deterioration of performance an OS environment that operates in a virtualization environment is reduced, and sufficient performance can be realized even though a plurality of OSs are operated on a existing server. A virtual machine that is generated by the virtual machine monitor can dynamically change computer resources of a CPU or a memory during the OS operation, and has availability higher than that of partitioning of hardware. In order to use a resource efficiently, it is considered to apply a function of a virtual machine monitor that changes a resource allocation dynamically.    Patent Document 1: Japanese Patent Application Laid-Open No. 2005-11331    Patent Document 2: Japanese Patent Application No. 2006-19409    Non-Patent Document 1: B. Dragovic, K. Fraser, S. Hand, T. Harris, A. Ho, I. Pratt, A. Warfield, P. Barham and R. Neugebauer, Xen and the Art of Virtualization, 19th ACM Symposium on Operating Systems Principles (SOSP19), 2003